Thomas h



(No Model.)

- n T, H. DUNHAM.

INSULATBD ELECTRICAL GONDUGTOB. No.' 280,366. Pat-enteduly 3, v1883.

3 V d. 0 r ./n.

' UNITED, STATES4 PATENT OFFICE.

THOMAS H. DUNHAM, OF BOSTON, MASSACHUSETTS.

? INSULATED ELECTRICAL CONDUCTOR.

SPECIFICATION forming pat of Letters'. Patent No. 280,366, dated Ju1yi3,1883,

Application filed June 12, 1882.

To all whvom it mag/concern: A Y

Be it known that I, THoMAs H. DUNHAM, of Boston, in the county ofSuffolk and State `of Massachusetts, have invented a new and usefulInsulated Electrical Conductor, of which the following is aspeciiication.

To make my new conductor a number of wires are laid parallel to eachother between two laps of raw cotton saturated with tar, asphalt, or thelike, the cotton laps being then compressed around the wires by suitablerollers. The tarred cotton lap provides a more perfect insulation, andits cost is much less than any covering heretofore used, so far as Iknow.

In the accompanying drawings, which illus trate a machine for making myimproved insulated conductor, Figure l is a side view, partly insection, ofthe whole machine. Fig. 2 is an end view of the wires incasedin the laps, passing through the severing-rolls. Fig. 3 isacross-section of one wire as severed from the rest. Fig. 4 shows thedevice for finishing the separate wires, and Fig. 5 is a cross-sectionof a finished conductor.

I do not coniinemyself to the particular machine shown in the drawings,as other devices for tarring the bats and inclosing the wires betweenthem may be found equally efficient.

In the present machine a vat, A, is surrounded by a vsteam-jacket, a,which is kept full of steam to heat the tar, asphalt, or the like, B,with which the vat is kept filledto the required depth. A series ofrollers, C O C2 C3 0*, are mounted in boxes secured to the side of thevat A. Two endless webs or aprons, DD', pass between these rollers andover the rollers l d. The rst pair of rollers, C, fit as closely as thenature of the liquid will allow aboutan opening in the end of the vatbelow the top of the liquid. A lap of raw cotton, E, wound on a reel ismounted on a stud, e, and a similar lap, E", is mounted lower down onthe same stand. A reel containing a number of coils of wire, F, ismounted on a stand, f, in a planebetween the rolls of lap E and EC Thelap from the lower roll, E', is first drawn through vat A and laidevenly O11 the lower web, D. The wires are then drawn from the coils,passed through holes in the guide-plate j", then over the lap E, onwhich they are laid and the wires placed between them.

(No model.)

equidistant from and parallel to each other. The upper lap, E, is nowdrawn over and evenly laid on the wires. The upper web, D, is thenlowered until it rests on the upper lap, and is held there by the upperrollers, which are placed in position as shown. The axles of the lowerrolls project through stuffing-boxes in one side of the vat, and are allgearedv to be revolved together in the same direction by a belt or anysuitable well-known connections. The vat is now iilled with hot tar orthe like, and as soon as the laps already in place are sufficientlysaturated the rolls are made to re- Volve, thereby drawing in thecontinuous laps The iirst rolls are smooth, and as they are adjustedmore or less closely, according to the viscidity of the tar about theopening in the vat, they, together with the partially-compressed laps,prevent any excessive leakage. The other rolls are provided withproperly-spaced grooves gradually increasing in depth. The last pair ofrollers are above the tar, and are held together by weights or springswith. sufcient force to squeeze out the surplus tar. the laps and wiresemerge cemented together, as shown at H in Fig. 2, containing about teninsulated wires for every foot in width of the laps, and may becollected in rolls of any desired size. Sixty or seventy yards in lengthmake a convenient roll for handling. In this shape my improvedconductors are admirably adapted for underground use, and can be readilylaid by simply spreading the roll iiat in a properly-prepared trench orbox,"or by rolling the fiat band edgewise to a cylindrical form andsecured at proper intervals. This covering not only provides insulation,but also cffectually protects the wires from the air and moisture.

It is often desirable to have single insulated wires both for overheadand underground use, and for this reason I pass the laps and theirinclosed wires, as they comefrom the squeezerolls, between the revolvingknives I I', (see Fig. 2,) and cut them in strips 7L, of equal width,each strip containing one wire, as shown in Fig. 3. By keeping theknives wet with water the tarred cotton is readily cut. These strips arethen passed through a steanrheated revolving former, K, by which the taris softened, and the wings or ribs are folded around From these rolls"which shows a number oi'l parallel wires covand cemented to thecovering` over the wire, and made round by being drawn through thecylindrical part 7c of the revolving former K. A remarkable strength isimparted t0 unspun cotton by saturating it with tar or the like, and myimproved covering` will resist all the strains and wear to whichoverhead wires are liable better than any covering that Iam acquaintedwith.

I am aware of English Patent N o. 2,707 of 1857, which shows abat orieece of raw cotton laid on a wire coated with an insulatingl materialwhile this insulating,` material is still soft, and an outer coating ofinsulatin gmateri al applied to the cotton-bat so laid 0n. I am alsoaware of English Patent No. 1,751 of 1866,

THOMAS II. DUNIIAM.

VWitnesses:

IVM. A. COPELAND, JOHN R. Snow.

